Haven't seen a lot from Guy, and going off memory, but he did quite well initially against Superman, even got some lip service for what it's worth(saying something like "I haven't been hit that hard since Doomsday!!" Although not the only time Superman's said stuff like this 😆 ) but still lost. They had another fight he did well against Superman in, but that could have been a recap of the fight I'm referring to. He looked superior to a Darkstar, the guy who was sorta the Hal of Darkstars. I don't have the scans handy(made them, but
need to fix my computer and may have lost them) and would have to go through the titles to get them, but Darkstars in general had done well against to beaten Flash(Pre-Speed Force discovery Wally), Professor Zoom (pretending to be Barry), various GLs(including matching a blast with Hal IIRC), Evil Star and his Starlings(GL villain), I think Doctor Polaris, the L.E.G.I.O.N.(individual members, but I want to say sometimes one against two or more), and Lar Gand in his Valor days. But the Darkstar Guy faced? He had come back from an alternate universe where he had a new suit that was actually more powerful than the suit all those examples I gave were done with, and I believe the upgraded suits they'd use when the Controllers left them would be based on it. The suit was causing him serious pain because it wasn't attuned to him or something like that, but I do believe he had it fixed by the time he fought Guy. I'm pretty sure Guy fought Lobo too, but it was one of those scenes where tons of characters are fighting simultaneously and we only see parts of the fights, like that big deciding factor brawl in JLA/AVENGERS where they fought over the last artifact.
Scans?
This one
https://static.comicvine.com/uploads/original/3/30145/3863770-git%27s+harder+than+doomsday.jpg
I'd call hyperbole
However he did this to Major Force
https://static.comicvine.com/uploads/original/3/30145/3863787-vs+major+force.jpg
He was somewhat pissed at the time.
Now another fight with Clark and Rampage (Clark was hokding vack because Guy was being influenced mentally by the tornaks a valdarian enemy)
https://static.comicvine.com/uploads/original/3/30145/3863804-vs+superman+and+rampage.jpg
https://static.comicvine.com/uploads/original/3/30145/3863805-vs+superman+and+rampage+2.jpg
https://static.comicvine.com/uploads/original/3/30145/3863806-vs+superman+and+ranmpage+3.jpg
Matrix Supergirl came along in the form of Ice to break him out od his delusions
Guy's durability is also pretty good. Another figjt with Supes in action 709 (or 710 somewhere around there) Clark froze him in liquid nitrogen. Jis shape shifting body formed armor to protect him. So while frozen solid he was still ok.
My favorite thing was the weapons he made from shape shifting.
https://static5.comicvine.com/uploads/original/3/30145/5661800-guy+gardner+%2325+-+page+22.jpg
https://static.comicvine.com/uploads/original/3/30145/5661798-guy+gardner+%230+-+page+9.jpg
I just dont know Ares enough to say who wins.
He also had better fights with Lobo as Valdarian shape shifting brick than a GL or Yellow Lantern